Although Palestine and Syria have been in Muslim hands since the 7th century, many of the inhabitants are still Christian. Moreover the region has in recent years been fought over by two rival Muslim powers, the Seljuk Turks and the Fatimid dynasty of Egypt. In these circumstances there is an element of welcome for the crusaders.

On June 7 they reach their destination, arriving outside the mighty walls of Jerusalem. The city is at present held by the Fatimids. In the heat of the summer the crusaders toil for five weeks building two huge siege towers. Finally, in mid-July, they push them into place. On July 15 they breach the walls.

The resulting massacre of the Muslims and the Jews of Jerusalem shocks even medieval public opionion. The only Muslims to escape are the garrison of the main keep of the city, the tower of David. For a large quantity of treasure they are allowed to leave unharmed.

All other Muslims are slaughtered wherever they may be, in streets or houses or holy places. Many lock themselves in one of their holiest shrines, the al-Aqsa mosque. Crusaders force the door and slay them. The Jews suffer a similar fate when they take refuge in their chief synagogue. It is burnt with them all inside. One of the crusaders describes these scenes in Jerusalem as a 'just and wonderful Judgement of God'.

The Latin kingdom of Jerusalem: 12th century

With the official purpose of the crusade achieved, in the recovery of Jerusalem and the Holy Sepulchre, attention turns to a problem of at least equal concern to many of the crusaders - how to establish feudal kingdoms in the captured territories, with fiefs of land distributed to nobles and their followers in due degree.

The administration of Palestine and Syria evolves over the next ten years, as more areas are annexed. By 1109 the region consists of four feudal states. Jerusalem is a kingdom, whose king is owed allegiance by the other three rulers. Antioch is a principality. Tripoli and Edessa are counties, the fiefs of hereditary counts.

These regions form a continuous strip along the east Mediterranean. The coastal towns benefit from increased trade as ships from Venice, Genoa and Barcelona arrive with supplies, reinforcements and pilgrims. They return home with the pilgrims and a cargo of eastern goods for the markets of the west.

Enabling pilgrims to reach the holy places of Palestine has been one of the main purposes of the crusade. Protecting pilgrims from illness or attack is seen as an important task for the crusaders once they are in Palestine (where they become known as the Franks, since the majority are French or Norman and their language is French). These duties prompt the founding of two famous orders of knighthood, the Knights of St John and the Templars.

The years before the fall of Edessa: 1099-1144

In the early years of the Latin kingdom the crusaders establish themselves in Palestine more securely than might have been expected. The Fatimids of Egypt attack Jerusalem in 1105 but are repelled. Thereafter the Latin kingdom seems to settle down as one power among many in an unsettled region, taking part in the endemic local warfare but not in any fanatically sectarian mood. Nor are the neighbouring states particularly inflamed against the Christians, in spite of the crusaders' appalling treatment of Muslim Jerusalem.

One exception to this surprising mood of tolerance is the Turkish governor of Mosul.

Zangi, the governor of Mosul, is a Mameluke appointed to his position in 1127 by the Seljuk Turks. He immediately begins to extend his power westwards, taking Aleppo in 1128. Recognizing that the presence of the crusaders can be used to unify the Muslims of this fragmented region under his own leadership, he urges a jihad against the intruders. The Arabic word means any struggle on behalf of Islam, the extreme form of which is a holy war.

From Aleppo, Zangi is well placed to threaten the elongated line of crusader states at a vulnerable point between Antioch and Edessa. But first he tries to make a more direct advance on Jerusalem, through Damascus.

Zangi fails to take Damascus, which is held by an independent Muslim dynasty, but eventually he strikes, in 1144, against Edessa. After a four-week siege the city falls to him, soon followed by the rest of this northern crusader territory. Zangi's campaign breaks the Christian barrier which for half a century has separated the Turks of Iran from the Turks of Anatolia.

The Muslims of the Middle East discover a new sense of purpose, while the loss of Edessa causes consternation in western Christendom. The pope preaches a second crusade, urging the kings and princes of Europe to go to the defence of their colleagues in the east.